THE FOLIC ACID GROUP 585 



per kg of diet is fatal to all the animals. The symptoms of the toxicity 

 include severe watery diarrhea, resulting in extreme dehydration, loss 

 of weight, porphyrin-stained whiskers and hemoconcentration. Signs of 

 nervous involvement and anoxia develop prior to death, and extensive 

 tissue changes, including intestinal lesions and a very hypoplastic bone 

 marrow, are observed. 129 In the peripheral blood, marked granulocyto- 

 penia and reticulocytopenia and a moderate lymphopenia develop simul- 

 taneously. 132 Very high concentrations of pteroylglutamic acid (20-30 

 mg per kg of diet) are required to prevent the effects of even the mini- 

 mum lethal concentration. The folic acid content of the liver appears to 

 be decreased as indicated by microbiological assay. 133 The LD 50 of the 

 analogue for rats receiving single doses is 4.5 ±1.4 mg per kg. 132 Regard- 

 less of the size of the dose above the minimum lethal dose, the course of 

 the fatal intoxication is not altered. The animals are unaffected for ap- 

 proximately one day, but all fatalities usually occur on the third or fourth 

 day. Oral administration is as effective as parenteral injection, and frac- 

 tional doses are cumulative and are possibly more effective than a single 

 dose. Animals surviving the minimum lethal dose have a transient re- 

 tardation in growth with subsequent rapid recovery. 



At a concentration of 0.3 mg per kg of diet, 4-amino-4-desoxyfolic 

 acid tends to lower slightly the hemoglobin and white cell count of 

 mice. 134 The effect is prevented by high concentrations of folic acid, but 

 the high mortality of mice fed 1 mg of the analogue per kg of diet is not 

 affected by folic acid even at high concentrations (100 mg per kg of diet). 

 Gross examination at autopsy revealed no lesions. 138 The LD 50 for mice 

 receiving a single dose of the analogue is 1.9 ±0.3 mg. per kg. 132 Frac- 

 tional doses were cumulative and almost as toxic as the single dose. The 

 LD 50 can be increased several fold by repeated administration of folic 

 acid (47 mg per kg daily) or pteroyltriglutamic acid (500 mg per kg 

 daily) before and after administration of the 4-amino analogue. Neither 

 thymine nor refined liver extract has such an effect on the toxicity of the 

 analogue. 132 



Guinea pigs given daily subcutaneous injections of 0.5 to 5.0 mg of 

 4-amino-4-desoxyfolic acid lose weight and with few exceptions die within 

 11 to 28 days. 135 The symptoms of the toxicity noted include normocytic 

 anemia, leucopenia, agranulocytosis, thrombocytopenia and hypoplasia 

 of the bone marrow. Although refined liver extract does not prevent the 

 anemia or leucopenia, folic acid in concentrations 25 to 100 times that 

 of the analogue appears to prevent the development of leucopenia or 

 thrombocytopenia, but not the anemia. 135 



The 4-amino analogue administered to dogs in daily doses of 0.05 to 

 0.1 mg per kg of body weight is fatal to approximately half the animals 



